Science
How does a compass work?
A compass works because its lightweight magnetic needle is free to rotate and aligns itself with Earth's magnetic field. One end always points toward magnetic north, giving you a reliable sense of direction anywhere on the planet.
See it in motion.
Watch a 2-minute animated lesson that shows exactly how a compass works.
Step by step
- 1The needle is a small magnet balanced to spin freely.
- 2Earth itself acts like a giant magnet, with field lines running north–south.
- 3The needle lines up with those lines, pointing to magnetic north.
- 4Magnetic north differs slightly from true north — a gap called declination.
- 5Nearby metal or magnets can disturb the reading.
Frequently asked questions
- Why does a compass point north?
- Its magnetized needle aligns with Earth's magnetic field, whose lines run roughly between the magnetic poles, so one end settles pointing north.
- Is magnetic north the same as true north?
- No. Magnetic north is where the field points; it sits some distance from the geographic North Pole, and the difference is called declination.
- Why does metal mess up a compass?
- Iron and magnets create their own local fields that pull the needle away from Earth's, giving a false reading.